To satisfy Admin1’s requirement, which action should you perform in the Azure portal?

The correct action is to modify the subscription's properties because Admin1 needs to change the directory associated with the subscription. This is done within the subscription's settings, specifically under its properties, where the directory can be transferred. Modifying Groups in Azure Active Directory (Azure AD) is incorrect because it deals with user and group management within a directory, not the directory linkage of a subscription. Modifying Properties in Azure AD is also incorrect as it pertains to the Azure AD tenant itself, not the subscription's association. Modifying Access control (IAM) settings is used for assigning roles and permissions within a subscription, not for changing the subscription's linked directory.